Apparatus for making a drilled hole with an undercut

Abstract

The drilling apparatus for making a drilled hole with an undercut includes a drive device for rotating a hollow drilling shaft (3); a drill bit holder (23,38) held in the hollow drilling shaft (3); a drill bit (4,26) having a drilling head provided with laterally projecting cutting edges (25) projecting from the drill bit holder (23,38); a device for swivelling out the drill bit holder (23, 38) with the drill bit from a drilling center line (5) including at least one control element of the drill bit holder, a sliding sleeve (11) surrounding the drilling shaft (3) and a swivelling-out element (21,39) connected to the movable sliding sleeve and engaging the control element to swivel out the drill bit holder (23, 38); and a device for raising and lowering the drive device (2) together with the drill bit holder (23,38) and the drill bit (4,26). In one embodiment the swivelling-out element is a sliding block and the control element is a cam surface in a slot provided in the drill bit holder.

I claim: 
     
       1. Drilling apparatus for making a drilled hole with an undercut, said drilling apparatus comprising a drive device (2) providing means for rotating a hollow drilling shaft (3);   a drill bit holder (23,38) held in the hollow drilling shaft (3) so as to be rotatable with said hollow drilling shaft (3);   a drill bit (4,26) having a drilling head provided with laterally projecting cutting edges (25), said drill bit (4,26) being held in said drill bit holder (23,38) so as to project from the drill bit holder (23,38);   means for swivelling out the drill bit holder (23, 38) with the drill bit from a drilling center line (5), said means for swivelling out comprising at least one control element of said drill bit holder, a sliding sleeve (11) surrounding the drilling shaft (3) and a swivelling-out element (21,39) connected to said sliding sleeve and engaging said control element to swivel out the drill bit holder (23, 38); and   means (1) for raising and lowering said drive device (2) together with said drill bit holder (23,38) and said drill bit (4,26).   
     
     
       2. A drilling apparatus as defined in claim 1, wherein said drill bit comprises a hard metal drilling plate (52) provided with the lateral cutting edges (25) for forming said drilled hole in a material selected from the group consisting of concrete, ceramics and stone. 
     
     
       3. A drilling apparatus as defined in claim 1, wherein the drill bit holder (23) is arranged to swivel about a swivel axis (24) oriented transversely to the drilling shaft (3). 
     
     
       4. A drilling apparatus as defined in claim 1, wherein the swivelling out element (21) is a sliding block (20), said control element is provided by a slot (22) formed in the drill bit holder (23), said slot (22) has a longitudinal extension in a longitudinal direction oriented at an acute angle to the drilling center line (5), said sliding block (20) is engaged slidably in said slot (22) and said slot (22) has a cam surface providing controlling cam means for controlling the motion of the sliding block (20) in the slot (22). 
     
     
       5. A drilling apparatus as defined in claim 1, wherein the means for swivelling out includes means for mounting the drill bit holder (38) in the hollow drilling shaft (3) so as to be movable parallel to the hollow drilling shaft, and the swivelling-out element (21) comprises a slider (39) movable axially in the drilling shaft (3) and having inclined control edges (41, 42). 
     
     
       6. A drilling apparatus as defined in claim 1, further comprising means for axially displacing the sliding sleeve (11) relative to the drilling shaft (3), said means for axially displacing comprising a spring element (17), a holding block (13) engaged with the spring element (17) and means for acting on the spring element (17) and the holding block (13), said means for acting including an operating lever (7) of the means (1) for raising and lowering, and a depth stop (14) for limiting a depth of the drilled hole attached to and projecting from the drilling shaft (3). 
     
     
       7. A drilling apparatus as defined in claim 6, wherein said means for axially displacing the sliding sleeve includes a holder (10) in which said sliding sleeve (11) is mounted and a tilting lever (9) mounted on the base plate (6) and engagable with the holder (10), and further comprising means for engaging the tilting lever (9) with the holder (10) against a spring force of said spring element (17) when the undercut is being formed and means for disengaging said tilting lever (9) from the holder (10), when the drilled hole with the undercut is completed. 
     
     
       8. A drilling apparatus as defined in claim 1, further comprising a locking mechanism (46) for locking the between the means (1) for raising and lowering and the holding block (13), a movable suction bell (49) surrounding the drill bit (4) and means for releasing the locking mechanism (46) between the holding block (13) and the means (1) for raising and lowering activatable by displacement of the movable suction bell (49) when a prescribed drilled hole depth has been reached. 
     
     
       9. A drilling apparatus as defined in claim 1, further comprising lock-against-raising means for preventing a return movement of the drill bit and drill bit holder until a required drilled hole depth has been reached and the undercut has been fully formed.